This application claims the priority of German Patent Document 102 03 917.8, filed on Jan. 31, 2002, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a steering column arrangement for a motor vehicle comprising an outer jacket tube, an inner jacket tube being displaceable within the outer jacket tube, and an adjusting device effective between the two jacket tubes for displacing one jacket tube in relation to the other jacket tube, the adjusting device comprising a drive unit and a servo component.
German Patent Document DE 195 24 196 C1 (corresponding to U.S. Pat. No. 5,690,362) discloses such a steering column arrangement. The known steering column arrangement has a steering spindle which supports a steering wheel and is mounted movably in terms of rotation in an inner jacket tube. The inner jacket tube is mounted inside an outer jacket tube in a telescopically displaceable fashion, the outer jacket tube being secured to the body support structure of the motor vehicle. An adjusting device is incorporated for displacing the inner jacket tube in relation to the outer jacket tube, said adjusting device being formed as a servo component taking the form of a spindle drive and being actuated by an electric motor. The spindle drive has a positioning spindle whose axis is parallel to the steering axis of the steering spindle and which runs along the outside of the outer and inner jacket tube, said spindle drive being positionally fixed on the inner jacket tube at one end face by means of a mounting. In the region of the outer jacket tube a threaded nut which is mounted between two energy-absorbing bearing blocks is seated on the positioning spindle which is formed as a threaded spindle. The electric positioning motor acts on the threaded nut via a corresponding toothed gearing. In the event of an impact load on the motor vehicle, additional impact energy can be absorbed in the region of the adjusting device by plastic deformation of the energy-absorbing bearing blocks through the introduction of forces through the adjusting spindle.
German Patent Document DE 198 12 179 C1 (corresponding to U.S. Pat. No. 6,264,239) discloses a further steering column arrangement, in which impact energy is absorbed by the adjusting device. This arrangement differs from the one described above in that the servo component running along the steering column axis is provided with a designated folding point, and in that a support bracket is provided at the height of the designated folding point, said support bracket being arranged in a positionally fixed manner on the inner jacket tube, extending at least partially over the designated folding point and being designed in a fashion permitting plastic deformation.
An aspect of the present invention is to create a steering column arrangement of the type described above, said steering column arrangement realizing a different principle of a safety steering column, in which impact energy is absorbed in the region of the adjusting device.
This aspect may be achieved in that the drive unit is releasably fastened to a guiding device and in that the drive unite is mounted so as to be displaceable along the guiding device.
According to this arrangement, the energy absorption does not take place in the region of the servo component of the adjusting device, but rather in the region of the drive unit of the latter. To this end the drive unit is releasably fastened to a guiding device, along which guiding device the drive unit is displaceably mounted under absorption of energy. This has the advantage that the absorption of energy occurs in conjunction with a defined motion of the drive unit along the guiding device. With this, the direction of motion is uniquely defined by the guiding device and is therefore predeterminable. Furthermore, as the energy absorption takes place during the motion of the drive unit in relation to the guiding device, i.e. during a defined motion, the extent and the profile of the energy absorption can be set particularly easily and accurately.
The guiding device can be assigned to a jacket tube, for example the outer jacket tube. The outer jacket tube is usually arranged fixed to the vehicle. This design has particular advantages for manufacturing, as it enables simple assembly of the guiding device on the jacket tube, as the latter is easily accessible. It is, of course, also conceivable for the guiding device to be assigned to a different vehicle component. The requirement is that this component does not move if a force is brought to bear on the steering column arrangement, said component being instead arranged in a positionally fixed fashion with regard to the vehicle.
According to one embodiment, the guiding device comprises at least one rail, the latter being aligned in the longitudinal direction of the steering column arrangement. The alignment in the longitudinal direction has the advantage that the drive unit also moves in a defined fashion in the longitudinal direction of the steering column arrangement. A guiding device which permits a motion of the drive unit in a different direction is also conceivable, but this would require greater build space.
For reasons of cost it is advantageous to have the guiding device and the jacket tube formed as a single part, as in this case the cost and effort of attaching the guiding device to the jacket tube are saved. Of course, an embodiment comprising a plurality of parts is also conceivable.
The drive unit can have receptacles assigned to the guiding configured. By way of the design of these receptacles, it is possible to define the resistance force opposing a displacement of the drive unit along the guiding device. In other words, by way of the receptacles it is possible to influence the extent of the energy absorption in a particularly simple manner.
The attachment of the drive unit to the guiding device can be configured in such a way that failure of the attachment occurs if a predetermined level of force being brought to bear on the steering column arrangement is exceeded. This embodiment represents a particularly simple way of activating the displacement of the drive unit and a simple way of activating the energy absorption. It is also conceivable for the attachment to be released depending on values measured by sensors, for example certain acceleration values.
Furthermore, it is also conceivable to assign an additional energy absorption element to the drive unit, which additional energy absorption element is then also activated if the drive unit is displaced in relation to the guiding device. In this way the extent of the energy absorption can be increased again. Depending on the type of energy absorption element chosen, the profile of the energy absorption can also be accurately set.
A metal element can be used, for example, as the energy absorption element, said metal element absorbing energy while being deformed. Such energy absorption elements are sufficiently well known and have the advantage that their deformation behavior and the energy required for and absorbed during the deformation process can be calculated with a high degree of accuracy. In this way, the extent of the energy absorption can be very accurately predetermined or set.
The energy absorption element can, for example, comprise a wire. A wire takes up little space, which is advantageous in terms of build space. It is furthermore conceivable to attach one end of the wire to the drive unit, so that a force is brought to bear on the wire at the moment when the drive unit starts to move. If the wire is routed around an obstacle, the wire is pulled around the latter at the moment when the force is brought to bear on the wire, and the wire deforms in the process. Energy is dissipated by this deformation. The profile and the extent of the energy absorption can be very easily set by the material and dimensions (cross section) of the wire.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.